Flat pole style sundials usually carry a style triangle. The straight edge is the actual style, the shadow of which indicates the hour.
The designer is otherwise free in his choice of shape.
As long as the sheet thickness is negligible, the hour lines may all be drawn from a single point without problems.
Things become different when the style triangle has appreciable thickness, actually defining two styles for which to draw hour lines.
Cutting the pattern in two and moving the halves out is not the correct way to adapt the sundial.
There exist otherwise beautiful sundials that were unfortunately so spoilt.
The correct way to adapt, for instance, a horizontal sundial is by moving the hour lines for 6 to 18 hours out, and those for the early morning and late afternoon hours, in.
The figure below pictures this.
Fer de Vries
English translation: RH